|
CLARK
MASTS
|
| A Diversion From Mast Manufacture - The Clark Scamp Moped of 1968 |
|
|
|
Mounted on the left hand side of the rear wheel, the 50 cc piston-ported 2-stroke engine featured radial finning on its alloy head and cast iron cylinder. The crankshaft was unusually constructed in that the flywheels bolted together by socket cap screws through the big-end bearing core with the con-rod seeming to run on uncaged roller bearings, so the whole assembly appeared to be home serviceable with no more than a simple Allen key! A Dansi flywheel magneto set was located on the nearside journal, while the drive was output to a simple single-stage centrifugal clutch.
On starting,
and once the motor got warm, the Both brakes proved suitably retarding when required, with the rear calliper function proving surprisingly effective, though generally small wheeled machines would typically be expected to deliver better hub braking performance in any case, due to the basic law of physics. The Scamp
proved to be an unhappy diversion for Alec Clark and his company,
however following discontinuation of the Scamp, the company's portable
air-operated telescopic mast business continued to thrive. Today Teksam NV and Clark Masts Teksam offer over 200 different models
of
Air-operated
portable masts
and
emergency
lighting systems.
The manufacturer of Clark Masts today, Teksam NV, is represented in Australia and the Asia-Pacific
region by Portable Masts
Australia Pty Ltd. |
ultimately
sold. The Scamp was a slight diversion for Alec Clark from his core business of
the manufacture of portable air-operated telescopic masts. The diversion,
however, was
short lived as a breach of confidence suit halted production in
November 1968. 
Scamp
Technical Details -
The Scamp was a
small wheeled bicycle with a gear-case in the rear wheel similar to that
of the BSA Winged Wheel. The engine being mounted onto the side of the
gear-case with the cylinder angled up towards the front at 45 degrees
and placed generally out into the air stream for reasonable cooling. The
Scamp's design used quite an unusual means of spinning the engine for
starting purposes. The final drive was by a large gear, driven by a pinion,
which ran in an oil bath. On the pinion shaft was a centrifugal
clutch drum which had a slot machined into it. On the centrifugal
clutch, which was mounted directly onto the crankshaft, there was a
plastic counterbalanced pawl that was lightly spring loaded to bring it
into contact with the clutch drum. As the machine was wheeled
forward, the clutch drum rotated and the plastic pawl engaged the slot
which in turn caused the engine to turn over. Once the engine was
running the centrifugal clutch rotated causing the pawl to overtake the slot
and, because it was counterbalanced, it pivoted out of contact with the
drum, leaving the engine idling but not driving the rear wheel. As
the engine was revved the centrifugal clutch transmitted drive to the rear
wheel and, with the help of a couple of pushes on the pedals, the Scamp
would get mobile.
The
rear 'disc' wheel was a primitive assembly comprising of a Dunlop
12"×2" rim bolted and riveted through the spoke
holes, to a pressed steel disc form, fixed to a driving flange. It
may be of little surprise to find that such wheels often displayed some
buckle effects. The flange rotated on bearings around the rear
axle, driven on a shaft from a large reduction gear running in an
oil-bath alloy case, and powered by a pinion shaft from the clutch drum.
Turning a "power key" located in the clutch housing enabled
the drive to turn the motor, by a counterbalanced nylon pawl engaged
through a slot in the clutch drum. Once the motor was started,
centrifugal force overcame a spring to disengage the pawl. The
automatic clutch engaged as motor revs were further increased.
Turning back the "power key" disabled the pawl as the clutch
rotated into contact, returning the Scamp to peddle bicycle mode.
Clark
Scamp cruised happily up to 25mph, above which, vibrations would start coming
in through the Radaelli seat and the ride became uncomfortable. Downhill, 34mph maximum
speed was occasionally achievable. Speed fell away
readily as the bike encountered any incline, but it usually still
managed to
labour slowly up moderate hills at low revs without the need to pedal.
